1. Field of the Invention
The invention herein relates to door and window latches, especially for sliding, pocket or bifold doors or windows.
2. Background Description
Sliding, pocket and bifold doors and windows have been fixtures of residential and commercial buildings for many years. For brevity throughout this application, such doors and windows and related structures will sometimes be referred to generically as "closures" and the embodiment exemplified and discussed will be a door. It will be understood, of course, that the invention applies equally to all such closures. Also for brevity, the term "sliding door" or "sliding closure," as used in the Specification and the claims herein, will be inclusive of all closures in which the closure at the point of final approach to the jamb moves in a plane perpendicular to the face of the jamb, rather than moving in a plane parallel to the face of the jamb as in characteristic of most "swinging" or "rollup" doors. Thus, for the purposes of this invention, the term "sliding door" encompasses not only those closures commonly classified in the trade as "sliding" (including those which commonly incorporate small caster wheels so that both rolling and sliding motions are involved), but also those normally referred to as "bifold," " pocket," "accordian," "folding" and similar designations.
Commonly the sliding door is formed of a door frame attached to the building structure and which includes two parallel internal U-shaped tracks in the top and bottom of the door frame. One-half of the door frame is occupied by a stationary panel, normally with its own frame surrounding an interior sheet of glass or screen, which is fixed in one track. The other half of the door frame is occupied by a moveable (sliding) panel, also with its own frame and interior sheet of glass or screen, which is seated in the second track and can be slid parallel to and past the fixed panel to open or close the door. As noted, smaller closures, particularly windows, have a moveable panel which only slides in its track, while larger closures, particularly doors, commonly incorporate small castor wheels into the bottom (and sometimes top) of the panel frame so that the moveable panel to some extent rolls in the track as well as slides.
It is normal practice to make the moveable panel slightly undersized as compared to the door frame, so that while the moveable panel is retained in the U-shaped tracks by contact at both its bottom and top, there is normally a small gap between the top of the moveable panel and the base of the top track. This allows one to remove the moveable panel from the door frame by lifting it slightly so that the bottom edge of the panel clears the lower track and the panel can then be swung outwardly and removed entirely from the door frame. This facilitates cleaning of the door, repair or replacement of damaged glass or screens, and interchange of moveable glass and screen panels when the seasons change.
In addition, the necessary ability to remove the moveable panel from the frame also creates a security risk, since it is also possible for a criminal to lift the door out of the track and thus gain entry a home, motel room or other place where such a door is mounted. In the past, there have been a number of proposals for preventing the door from being removed from the track other than when removal is desired by the occupant of the building. However, many such proposed devices have been cumbersome, unattractive or ineffective.
In recent years there has been considerable concern about the safety of home and motel swimming pools, to which people commonly have access from inside a house or motel room by means of a sliding door. There have been a number of unfortunate incidents where small children have gone out through the sliding door and have fallen into the pool and drowned before other occupants of the house realized the children had opened the door and gone out to the pool area. Consequently, a number of states, counties and municipalities are currently considering enacting building and safety regulations which would require new residential and commercial construction to make all sliding doors which open to a pool area close promptly and automatically after being opened. Retrofitting existing pool access sliding doors is also under consideration. (A unique and highly effective mechanism for automatic closure of sliding doors is described and claimed in pending U.S. patent application Ser. No. 07/724,822, filed by D.G. Hutchison and D.M. Prochaska on Jul. 2, 1991, and to which the latch of this invention is applicable.) Such automatically closing doors must, of course, have latch mechanisms which are automatically secured upon closure.
It would therefore be advantageous to have a latch mechanism which provides for simple and secure latching automatically when the sliding door is closed, which permits the door to be secured from attempts to remove it from the track, which can be easily unlatched when desired, and which is readily adaptable to sliding doors and windows of various configurations and which functions equally well whether the door or window closes and latches to the left or to the right. It would also be desirable to have means incorporated in the latch to prevent the door from being unlatched inadvertently or without authorization and to permit the latch to be held open when desired so that the door would not inadvertently become latched. It would also be advantageous to have the latch be capable of serving as either the main latching mechanism for the door or as an auxiliary (or "safety") latch which is incorporated into the door in addition to the main latching mechanism.